The present invention relates to an internal combustion engine air intake regulating system.
As is known, motor vehicles feature an air intake manifold fitted with an air supply regulating valve--generally a throttle valve--at which is formed a bypass conduit for additional air, and the angular position of which is user-controlled either directly (accelerator pedal) or indirectly (electronic control system activated by the accelerator pedal). The bypass conduit is in turn fitted with a second valve for regulating air supply to the engine independently off the user, and which is particularly useful for supplying the engine with additional air at idling speed, startup, or when the vehicle is "braked" by the engine upon release of the accelerator pedal ("dashpot" conditions).
Known engine air intake regulating systems provide for feedback control of the air supply along the intake manifold, i.e. for continuously detecting air supply due to the angular position of the throttle, by detecting either the air pressure along the intake manifold, or the electrical resistance of a potentiometer, which is closely related to the angular position of the throttle. In most known systems, no feedback control is provided of the air supply along the bypass conduit, so that no information relative to performance and the efficiency of the adjustment effected along the bypass is supplied to the system controlling the second valve. For example, in the case of known systems featuring a step motor for controlling the second valve, air supply can only be determined by the control system on the basis of the steps commanded by it to the step motor. As step motors, however, are known, under certain conditions, to "fall out of step", thus resulting in a discrepancy --"undetected" by the control system--between the number of steps commanded and those actually performed, and since the additional air supply parameter serves for processing further engine control data, any computing errors relative to additional air supply obviously result in data processing errors.
In certain engine air intake regulating systems, the additional air supply is feedback-controlled by detecting the electrical resistance of a potentiometer, which is closely related to the position of the second valve. Such systems, however, are expensive to produce, mainly due to the cost of the potentiometer, and the difficulties posed by suitably seating and assembling it.